• MANISH DEBBARMA

      Articles written in Bulletin of Materials Science

    • Structural, mechanical and optoelectronic properties of cubic Be$_x$Mg$_{1−x}$S, Be$_x$Mg$_{1−x}$Se and Be$_x$Mg$_{1−x}$Te semiconductor ternary alloys: a density functional study

      BIMAL DEBNATH MANISH DEBBARMA DEBANKITA GHOSH SAYANTIKA CHANDA RAHUL BHATTACHARJEE SURYA CHATTOPADHYAYA

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      Structural,mechanical and optoelectronic features of cubic Be$_x$Mg$_{1−x}$S, Be$_x$Mg$_{1−x}$Se and Be$_x$Mg$_{1−x}$Te alloyshave been explored by DFT-based FP-LAPW approach. Nonlinear reduction in lattice constant, but increment in bulk modulus and each of the elastic constants $C_{11}$, $C_{12}$ and $C_{44}$, occurs with increasing Be-concentration $x$ in each system. All the specimens exhibit elastic anisotropy. Specimens at $x = 0.0$, 0.25 and 0.50 show ductility, but remaining specimens at $x = 0.75$ and 1.0 show brittleness. Each ternary alloy is a direct ($\Gamma$−$\Gamma$) band gap ($E_{\rm g}$) semiconductor. Almost linear decrease in $E_{\rm g}$ with increase in $x$ is observed in each alloy system. Ionic bonding exists among the constituents of all specimens. The occupied valence chalcogen-p as initial and unoccupied conduction Be-3s, 2p and Mg-4s, 3p as final states play a keyrole in optical transitions. Nature of variation of zero-frequency limit in each of the $\epsilon_1(\omega)$, $n(\omega)$ and $R(\omega)$ spectra with $x$ isopposite to, while critical point in each of the $\epsilon_2(\omega)$, $k(\omega)$, $\sigma(\omega)$ and $\alpha(\omega)$ spectra with $x$ is similar to, the nature of variation of $E_{\rm g}$ with $x$.

    • Density functional study of elastic and thermal properties of cubic mercury-zinc-chalcogenide ternary alloys

      MANISH DEBBARMA SUBHENDU DAS BIMAL DEBNATH DEBANKITA GHOSH SAYANTIKA CHANDA RAHUL BHATTACHARJEE SURYA CHATTOPADHYAYA

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      First principle calculations of elastic and thermal properties of zinc-blende specimens within Hg$_x$Zn$_{1–x}$S, Hg$_x$Zn$_{1-x}$Se and Hg$_x$Zn$_{1-x}$Te ternary systems are executed. Elastic stiffness constants decrease non-linearly with increasing Hg-concentration in each system. Each cubic sample is mechanically and dynamically stable, elastically anisotropic, compressible against elastic deformation, ductile and fairly plastic. Hardness of specimens in each system reduces with enhancement in Hg-composition. Mixed kind of bonding with dominancy of covalent over ionic in most cases, bond bending over stretching and central type of interatomic bonding forces are calculated. In each system,covalency, Debye temperature and frequency, Debye temperature for acoustic phonon, thermal conductivity and melting temperature of specimens decreases, while Philip ionicity and Gruneisen parameter increases with enhancingHg-concentration.

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